1. Field of the Invention
The present invention relates to a fuel supply control method and apparatus for an internal combustion engine.
2. Description of the Prior Art
In one known fuel supply control method, the engine running speed and the intake manifold pneumatic pressure are detected and then used to calculate the basic pulse width of an injection signal to be applied to the fuel injectors. This basic pulse width is corrected in accordance with other engine operating parameters such as the exhaust-gas oxygen concentration, coolant temperature, atmospheric temperature, and degree of acceleration. The corrected pulse-width is used to adjust the actual fuel feed.
In general, a two-dimensional function table indicative of the relationship between the basic pulse width and the intake manifold pneumatic pressure and engine running speed is provided in a storage device beforehand. A basic pulse width corresponding to the detected engine parameters is found from this function table by interpolation.
Since the maximum value of the basic pulse width is about 7 msec, each item of the function table must be composed of two or more bytes (assuming a byte of 8 bits) in order to obtain accurate data on the basic pulse width. Composing each item of the two-dimensional function table by two or more bytes, however, leads to an extreme increase in the cost of the storage device.